Process for Producing an Adhesion-Promoting Layer on a Surface of a Titanium Material

ABSTRACT

A method for producing an adhesion promoting layer on a surface of a titanium material involves introducing the surface into an aqueous alkaline solution of sodium hydroxide at a concentration in a range from 100 to 300 g/l, sodium tartrate at a concentration in a range from 20 to 200 g/l, methyl glycine diacetic acid trisodium at a concentration in a range from 5 g/l to 60 g/l, and pentasodium triphosphate at a concentration in a range from 2 g/l to 20 g/l. A voltage is applied between the solution and the titanium material for a predefined period of time, in order to produce the layer by anodic oxidation of the surface.

BACKGROUND AND SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention relate to a method for producing an adhesion promoting layer on a surface of a titanium material; an adhesion promoting layer, according to the method, on the surface of a titanium material; as well as the use of an alkaline solution.

The production of adhesion promoting layers on a surface of a titanium material is known. The adhesion promoting layer can be used to join organic materials, such as adhesives, paint, sealants and/or the like, to the titanium material. The adhesion promoting layer on the surface of the titanium material can be produced, for example, by means of anodic oxidization; that is, the adhesion promoting layer can consist, for example, of an oxide layer. This oxide layer may be used as the adhesion promoting layer for a subsequent coating of the titanium material with the organic material. U.S. Pat. No. 4,473,446 discloses a method for treating the surface of titanium parts prior to adhesive bonding by anodization in a chromic hydrofluoric acid bath at an anodizing voltage ranging from one volt to 5 volts.

U.S. Pat. No. 4,394,224 discloses a method for treating titanium parts or titanium alloy parts in order to generate an adhesion promoting oxide layer. This method includes the steps of: applying to the surface and treating the surface with a mixture of aqueous solutions comprising sodium hydroxide and hydrogen peroxide; maintaining the applied mixture within a temperature range, in which the hydrogen peroxide is relatively stable; and causing an increased rate of oxidation on the surface area.

German patent document DE 34 27 543 A1 relates to an alkaline bath for the treatment of titanium. The bath is composed of an alkali hydroxide, a titanium complexing agent, and an impurity ion complexing agent. U.S. Pat. No. 3,907,609 discloses a chemical conversion process and a composition for producing an adherent conversion coating on titanium and titanium alloys. U.S. Pat. Nos. 5,814,137 and 6,037,060 relate to a surface treatment, preferably for titanium and aluminum alloys, in order to form a sol gel film, which adheres to the metal surface by means of covalent bonds, in order to generate a strong and durable adhesive bond between the metal and an organic adhesive without using toxic chemicals and while at the same time significantly reducing and/or eliminating the rinse water requirements of conventional anodizing and/or etching processes.

German patent document DE 38 02 043 C1 relates to a method for preparing a metal surface. In order to bond to plastic, a layer is applied to a metal surface by sandblasting with a material consisting of 0.1 to 30% by weight of an optionally silanized, amorphous silicon containing material having a grain size of less than 1 μm, and the rest of the material is a sandblasting medium having a mean grain size of greater than 1 μm, and this layer is subsequently silanized, if desired.

German patent document DE 10 2006 045 951 A1 relates to a method for the chemical modification and/or activation of the solid surfaces. In this method that employs at least one carrier medium, which is used to feed energy into the surface and to supply the surface with one or more halogen-containing compounds, the supply of the halogen containing compounds is carried out with a simultaneous addition of organosilicon compounds or silanes or organometallic compounds or silicon hydrides or metal hydrides to the carrier material. An application, which was filed by the same applicant and has the official application number 10 2010 054 473.6, relates to a method for promoting the adhesion of a surface of a titanium material. In this case the method generates an adhesion promoting layer, which is securely bonded to the surface of the titanium material and contains nanotubes, comprising titanium dioxide (TiO2), on the surface, and applies in an adherent manner an organic material to the adhesion promoting layer that comprises the nanotubes.

Exemplary embodiments of the present invention are directed to an alternative method that is designed to produce an adhesion promoting layer on a surface of a titanium material and for which the implementation requires only or at least predominantly environmentally compatible chemicals.

In accordance with exemplary embodiments of the present invention, the method for producing an adhesion promoting layer on a surface of a titanium material comprises the introduction of the surface into an aqueous alkaline solution comprising sodium hydroxide at a concentration in a range from 100 to 300 g/l, sodium tartrate at a concentration in a range from 20 to 200 g/l, methyl glycine diacetic acid trisodium at a concentration in a range from 5 g/l to 60 g/l, and pentasodium triphosphate at a concentration in a range from 2 g/l to 20 g/l; and the application of a voltage between the solution and the titanium material for a predefined period of time, in order to produce the layer by means of anodic oxidation of the surface.

The sodium hydroxide is present preferably at a concentration in a range from 150 to 285 g/l, even more preferred 175 to 270 g/l, 195 to 250 g/l, 210 to 240 g/l, 238 to 242 g/l, and in particular 240 g/l.

The sodium tartrate is present preferably at a concentration in a range from 20 to 200 g/l, even more preferred 60 to 140 g/l, 75 to 125 g/l, 85 to 110 g/l, 90 to 105 g/l, and in particular 100 g/l.

The methyl glycine diacetic acid trisodium is present preferably at a concentration in a range from 10 to 50 g/l, even more preferred 15 to 40 g/l, 20 to 35 g/l, 25 to 33 g/l, 28 to 32 g/l, and in particular 30 g/l.

The pentasodium triphosphate is present preferably at a concentration of 3 to 17 g/l, even more preferred 4.5 to 13 g/l, or 6 to 10 g/l, or 7 to 8 g/l, or in particular 7.5 g/l.

Any of the aforementioned concentration ranges or any concentration of one of the components of the solution can be combined with any concentration range or any other concentration of any other component.

It has been found that an adhesion promoting layer formed as a layer of oxide can be created on the surface of the titanium material by means of anodic oxidation of the surface of the titanium material in the specified alkaline solution in such a way that the adhesion promoting layer exhibits adhesion promoting properties that are at least as good as those of the state of the art. One advantageous feature is that exclusively or at least predominantly environmentally compatible active ingredients are necessary for this bonding purpose. Sodium hydroxide contains Na+ ions that are known from conventional common salt. Pentasodium triphosphate, also known as triphosphate, is a component of biological compounds, such as adenosine triphosphate. In addition, pentasodium triphosphate is also approved as a food additive. Thus, in comparison to the chemicals used in the prior art, a particularly harmless substance, i.e. methyl glycine diacetic acid trisodium, also known as the sodium salt of methyl glycine diacetic acid, is used, in particular, as a cleaning agent, in particular, as a dishwashing detergent and, is therefore, recognized as safe with respect to environmental considerations. Methyl glycine diacetic acid is also known by the name MGDA. Sodium tartrate is a sodium salt of tartaric acid, also approved as a food additive and, therefore, also recognized as especially safe with respect to environmental considerations. The sodium tartrate acts in the alkaline solution as a titanium complexing agent and, as a result, can advantageously improve the redissolution properties. The methyl glycine diacetic acid trisodium acts as an impurity ion complexing agent; and the pentasodium triphosphate acts as a skeleton former. One advantage is that the alkaline solution is totally fluoride free and yet still allows an optimal pretreatment of the surface of the titanium material for a durable, high strength bonding between organic coatings. The term titanium material may be understood to mean pure titanium or a titanium alloy, such as a titanium alloy, which is known as Ti6Al4V.

In another embodiment of the method the anodic oxidation is carried out advantageously with a voltage in a range from 2 to 50 V, preferably 3 to 45 V, 5 to 35 V, 7 to 25 V, 9 to 20 V, 9 to 15 V, 10 to 12 V, and in particular 10 V. The advantageous oxide layer can be generated at the specified voltage.

In an additional embodiment of the method, the anodic oxidation of the surface is carried out advantageously for a period of time, in which the advantageous adhesion promoting layer can be generated on the surface of the titanium material. In this case the duration of time is in a range from 5 to 60 min., preferably 8 to 50 min., 11 to 40 min., 15 to 30 min., 18 to 25 min., 19 to 22 min., and in particular 20 min.

Another embodiment of the method provides the anodic oxidation advantageously at a maximum current density, at which the advantageous adhesion promoting layer can be generated on the surface of the titanium material. The maximum current density is in a range from 0.2 to 10 A/dm2, preferably 0.4 to 8 A/dm2, 0.6 to 4 A/dm2, 0.8 to 2 A/dm2, 1.0 to 1.5 A/dm2, 1.1 to 1.3 A/dm2, and in particular 1.2 A/dm2.

An additional embodiment of the method provides the anodic oxidation advantageously at a temperature, at which the advantageous adhesion promoting layer can be generated on the surface of the titanium material. The temperature is in a range from 5 to 60° C., preferably 10 to 50° C., 15 to 40° C., 20 to 35° C., 25 to 33° C., 28 to 32° C., and in particular 30° C.

Any range or any value of one of the aforementioned features can be combined with any range or any value of any other feature or with any combination of concentration ranges or concentrations of the dissolved components.

Another embodiment of the method provides an anodic oxidation of the surface in the alkaline solution and, as a result, the generation of an oxide layer having a layer thickness in a range from 50 to 600 nm, preferably 70 to 400 nm, 100 to 250 nm, and in particular 150 nm. In this case the advantage is that extremely good adhesion can be generated at the specified layer thickness.

Exemplary embodiments of the present invention are also directed to an adhesion promoting layer, which can be produced or is produced according to a method described above, on a surface of a titanium material as well as by means of a titanium material. The surface of the titanium material has, in particular, a porous nanostructure with adjacent protrusions with undercuts, and, in particular, an interference color. The individual structures are in the order of 50 to 300 nm. The adhesion promoting layer on the surface of the titanium material can be coated and/or can be provided advantageously with an organic material for long term stability and with extremely good adherent properties. In addition, it can also be detected by means of the interference color that the desired adhesion promoting layer is actually present on the surface of the titanium material or more specifically that the titanium material has the adhesion promoting layer on its surface. Moreover, the results are the advantages described above.

Exemplary embodiments of the present invention are also directed to the use of an aqueous alkaline solution with a method described above. The results are the advantages described above.

Additional advantages, features and details shall become apparent from the following description, in which at least one embodiment is described in detail with or without reference to the drawings. Described and/or graphically illustrated elements form alone or in any logical combination the subject matter of the invention, optionally also independently of the claims, and may also be additionally the subject matter of one or more separate application(s). Identical, similar and/or functionally equivalent parts are provided with the same reference numerals.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

In the drawings

FIG. 1 is a schematic view of a device for carrying out a method for anodic oxidization of a surface of a titanium material in an alkaline solution.

FIG. 2 is a plan view of an oxide layer, nano-structured by means of anodic oxidation, on the surface of a titanium material; and

FIG. 3 shows a cryo-fracture of the surface, depicted in FIG. 2, on the titanium material.

DETAILED DESCRIPTION

FIG. 1 shows a schematic view of a device 1 for producing an adhesion promoting layer on a surface 3 of a titanium material 5. The device 1 comprises a bath 7 with an electrolyte 9. The electrolyte 9 comprises sodium hydroxide, sodium tartrate, methyl glycine diacetic acid trisodium as well as pentasodium triphosphate in an aqueous solution. In order to generate an oxide layer, which is not shown in detail in FIG. 1, the titanium material 5 and the bath 7 are connected to an electric energy source 11. In so doing, an electric circuit is closed by way of the electrolyte 9 of the bath 7. The electric energy source 11 delivers a voltage 13, which produces a current 15 in the electric circuit that is closed by way of the electrolyte 9. If desired, control and/or regulating devices (not shown in detail) for adjusting the voltage 13 and/or the current 15 may be provided.

The device 1 can be used to generate, by means of anodic oxidation, an oxide layer 17 (which is shown in FIGS. 2 and 3) on the surface 3 of the titanium material 5. The scales, shown in FIGS. 2 and 3, are drawn in each instance with a line that gives the length in nm.

The adhesion promoting layer is produced on the surface 3 of the titanium material 5 by means of anodic oxidization. For this purpose, the surface 3 is introduced first into the bath 7 containing the alkaline solution or more specifically the electrolyte 9, for example, by at least partially immersing the titanium material 5 in the electrolyte 9. In the introduced state of the surface 3 the voltage 13 is produced between the electrolyte 9 and the titanium material 5 for a predefined period of time, in order to produce the layer by anodic oxidation of the surface 3 of the titanium material 5.

FIG. 2 shows a plan view of the surface 3 of the titanium material 5.

FIG. 3 shows a cryo-fracture of the titanium material 5 together with the surface 3, and at the same time the oxide layer 17 can be seen. A double arrow 19 in FIG. 3 symbolizes the thickness of the oxide layer 17, where in this case the thickness is about 150 nm.

It is clear from FIGS. 2 and 3 that the oxide layer 17 has a distinct microporous nanostructure, which exhibits nodular growths that are arranged next to one another. The nodular growths have a dimension of less than 300 nm, in particular less than 250 nm, in particular less than 200 nm, in particular less than 150 nm, preferably less than 50 nm to 100 nm and form an advantageous microporous surface.

Preferred Exemplary Embodiment

In order to produce the oxide layer 17, shown in FIGS. 2 and 3, on the surface 3 of the titanium material 5, the bath 7 is filled with the electrolyte 9 having a composition of 240 g/l of sodium hydroxide, 100 g/l of sodium tartrate, 30 g/l of methyl glycine diacetic acid trisodium, and 7.5 g/l of pentasodium triphosphate.

The surface 3 of the titanium material 5 is introduced, in particular immersed, at least partially in the bath 7.

The voltage 13 of 10 V is applied to the at least partially immersed titanium material 5 and the bath 7 by means of the electric energy source 11. The current 15 is adjusted in such a way that the surface 3 of the titanium material 5 exhibits a current density of up to 1.2 A/dm2. The voltage 13 and the current 15 and, thus, the current density of 1.2 A/dm2 are maintained for a duration of 20 minutes. The bath 7 is kept at a specified temperature of 30° C. If desired, devices (not shown in detail) for adjusting the temperature, for example, a heating unit and/or cooling system, may be provided in order to set the temperature to 30° C.

In summary, the desired nano structured surface 3, i.e. the oxide layer 17, can be obtained in a completely fluoride free process for the pretreatment of the titanium material 5 in order to achieve a durable, high strength bonding between the organic coatings.

Such a bonding can be achieved in an advantageous way by means of the micro-structured and/or nano-structured oxide layer 17. The described porous surface morphology can be generated advantageously on the titanium material 5. This titanium material can be coated in an adherent manner, for example, with organic materials, such as adhesives, paint, sealants and/or the like.

Advantageously the electrolyte 9 is not only fluoride free, but also contains exclusively or at least predominantly environmentally compatible active ingredients that are particularly biodegradable.

The interference color can serve as proof that the treatment was carried out and/or can serve as an identifier for the respective treated components made of the titanium material 5.

As an alternative and/or in addition, the oxide layer 17 on the surface 3 of the titanium material 5 can also be used for bonding biological material, for example, to implants.

As an alternative and/or in addition, it is conceivable that the solution comprises ions of other components, in particular ions of the same period of a periodic table; and these ions are present at least in traces and/or as at least a partial substitution.

The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof

LIST OF REFERENCE NUMERALS

-   1 device -   3 surface -   5 titanium material -   7 bath -   9 electrolyte -   11 electric energy source -   13 voltage -   15 current -   17 oxide layer -   19 double arrow 

1-13. (canceled)
 14. A method for producing an adhesion promoting layer on a surface of a titanium material, the method comprising: introducing the surface into an aqueous alkaline solution comprising sodium hydroxide at a concentration in a range from 100 to 300 g/l, sodium tartrate at a concentration in a range from 20 to 200 g/l, methyl glycine diacetic acid trisodium at a concentration in a range from 5 g/l to 60 g/l, and pentasodium triphosphate at a concentration in a range from 2 g/l to 20 g/l; and applying a voltage between the solution and the titanium material for a predefined period of time, in order to produce the adhesion promoting layer by anodic oxidation of the surface.
 15. The method of claim 14, wherein the sodium hydroxide is present at a concentration in a range from 150 to 285 g/l.
 16. The method of claim 15, wherein the sodium hydroxide is present at a concentration in a range from 175 to 270 g/l, 195 to 250 g/l, 210 to 240 g/l, or 238 to 242 g/l.
 17. The method of claim 16, wherein the sodium hydroxide is present at a concentration of 240 g/l.
 18. The method of claim 14, wherein the sodium tartrate is present at a concentration in a range from 20 to 200 g/l.
 19. The method of claim 18, wherein the sodium tartrate is present at a concentration in a range from 60 to 140 g/l, 75 to 125 g/l, 85 to 110 g/l, or 90 to 105 g/l.
 20. The method of claim 19, wherein the sodium tartrate is present at a concentration of 100 g/l.
 21. The method of claim 14, wherein the methyl glycine diacetic acid trisodium is present at a concentration in a range from 10 to 50 g/l.
 22. The method of claim 21, wherein the methyl glycine diacetic acid trisodium is present at a concentration in a range from 15 to 40 g/l, 20 to 35 g/l, 25 to 33 g/l, or 28 to 32 g/l.
 23. The method of claim 22, wherein the methyl glycine diacetic acid trisodium is present at a concentration of 30 g/l.
 24. The method of claim 14, wherein the pentasodium triphosphate is present at a concentration of 3 to 17 g/l.
 25. The method of claim 24, wherein the pentasodium triphosphate is present at a concentration of 4.5 to 13 g/l, or 6 to 10 g/l, or 7 to 8 g/l.
 26. The method of claim 25, wherein the pentasodium triphosphate is present at a concentration of 7.5 g/l.
 27. The method of claim 14, wherein the anodic oxidation is carried out with a voltage in a range from 2 to 50 V.
 28. The method of claim 27, wherein the anodic oxidation is carried out with a voltage in a range from 3 to 45 V, 5 to 35 V, 7 to 25 V, 9 to 20 V, 9 to 15 V, or 10 to 12 V.
 29. The method of claim 28, wherein the anodic oxidation is carried out with a voltage of 10 V.
 30. The method of claim 14, wherein the anodic oxidation is carried out for a period of time in a range from 5 to 60 min.
 31. The method of claim 30, wherein the anodic oxidation is carried out for a period of time in a range from 8 to 50 min., 11 to 40 min., 15 to 30 min., 18 to 25 min., or 19 to 22 min.
 32. The method of claim 31, wherein the anodic oxidation is carried out for a period of time of 20 min.
 33. The method of claim 14, wherein the anodic oxidation is carried out at a maximum current density in a range from 0.2 to 10 A/dm².
 34. The method of claim 33, wherein the anodic oxidation is carried out at a maximum current density in a range from 0.4 to 8 A/dm², 0.6 to 4 A/dm², 0.8 to 2 A/dm², 1.0 to 1.5 A/dm², or 1.1 to 1.3 A/dm².
 35. The method of claim 34, wherein the anodic oxidation is carried out at a maximum current density of 1.2 A/dm².
 36. The method of claim 14, wherein the anodic oxidation is carried out at a temperature in a range from 5 to 60° C.
 37. The method of claim 36, wherein the anodic oxidation is carried out at a temperature in a range from 10 to 50° C., 15 to 40° C., 20 to 35° C., 25 to 33° C., or 28 to 32° C.
 38. The method of claim 37, wherein the anodic oxidation is carried out at a temperature of 30° C.
 39. The method of claim 14, wherein the anodic oxidation of the surface is carried out in the alkaline solution while generating an oxide layer having a layer thickness in a range from 50 to 600 nm.
 40. The method of claim 39, wherein the anodic oxidation of the surface is carried out in the alkaline solution while generating an oxide layer having a layer thickness in a range from 70 to 400 nm or 100 to 250 nm.
 41. The method of claim 40, wherein the anodic oxidation of the surface is carried out in the alkaline solution while generating an oxide layer having a layer thickness of 150 nm.
 42. An adhesion promoting layer on a surface of a titanium material, the adhesion promoting layer being producible or produced by introducing the surface into an aqueous alkaline solution comprising sodium hydroxide at a concentration in a range from 100 to 300 g/l, sodium tartrate at a concentration in a range from 20 to 200 g/l, methyl glycine diacetic acid trisodium at a concentration in a range from 5 g/l to 60 g/l, and pentasodium triphosphate at a concentration in a range from 2 g/l to 20 g/l and applying a voltage between the solution and the titanium material for a predefined period of time, in order to produce the adhesion promoting layer by anodic oxidation of the surface, wherein the adhesion promoting layer has a porous nanostructure with adjacent protrusions with undercuts as well as an interference color. 